dont fail empty payload

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

proto.go

@@ -57,6 +57,8 @@ func (c *protoCodec) ReadBody(conn io.Reader, b interface{}) error {
 		buf, err := ioutil.ReadAll(conn)
 		if err != nil {
 			return err
+		} else if buf == nil {
+			return nil
 		}
 		return proto.Unmarshal(buf, m)
 	}